Laboratory for Thin Films & Photovoltaics
CuIn1-xGaxSe2 – Flexible and Lightweight
Solar cells based on CuIn1-xGaxSe2 absorbers show the highest efficiencies and performance stabilities among all thin-film technologies. Empa has developed a deposition process for CIGS thin-film solar cells which is suitable for high-speed and in-line production on low-cost substrates. Main research topics include:
- band gap and interface engineering of the CIGS absorber in order to find the optimum tradeoff between highest device efficiency and cost-effective mass production
- development of processes for other constituent layers
- multijunction (tandem) solar cells
The development of highly efficient, stable, light weight and flexible solar cells is important for terrestrial as well as for space applications. Our laboratory is developing a novel low temperature deposition process for the production of solar cells on flexible polymer foils. The thickness of the completed solar cell including the polymer substrate is less than 25 um. A world record efficiency of 20.4% was recently achieved. More...
CdTe Solar Cells
Lowest solar module production costs on the global PV market have been achieved with CdTe based technology. Our lab is pioneering the development of low-temperature processes (< 450°C) for both superstrate and substrate configuration enabling fabrication on various substrate materials. This allows to further reduce the production costs of CdTe solar cells in the future.
We are also involved in the development of flexible CdTe solar cells on polymer films and metal foils. We have demonstrated CdTe solar cells with efficiencies of 13.8% on flexible polyimide film and 10.9% on flexible steel foil. Our low-temperature processes are suitable for high throughput roll-to-roll manufacturing. More...
Tandem Cells – Solar devices with efficiencies towards 30%
A promising approach to reach efficiencies of 30% and above are the multijunction solar cell concepts. The main challenge in that case is the development of highly efficient wide band gap solar cells with both electrical contacts transparent. We are developing tandem solar cells with the novel technology based on trihalide organo-metal perovskite absorber combined with our highly efficient CIGS technology. More...
Alternative Materials and Processes
Solar cells made from Cu2ZnSn(Se,S)4 are a promising alternative to other thin film technologies using non-toxic and readily available materials. Using two different precursor synthesis routes (non-vacuum, 11.7% and vacuum, 9.4%), we investigate the origin of the VOC-deficit of kesterite absorbers.
The demanded properties of advanced coatings extend well beyond the characterisitcs of transparency and/or conductivity and aim at multi-functionality: element diffusion barriers, moisture and corrosion resistent barriers, control of electronic transport at interfaces, texturing for efficient light trapping. Investigated materials include metals, oxides (SiO2, TiO2, In2O3- or SnO2-based) and nitrides (SiN, Ti3N4) deposited by PVD and non-vacuum methods.
We are also developing solid state electrolytes for batteries which offer a new route towards compact batteries with a high energy density. More...
Functional Inorganic Materials
The recently founded group for inorganic thin film materials has the aim to connect fundamental research with applied research in the field of synthesis and self-assembly of inorganic thin film materials, with specialization on colloidal nano-structures. To improve this interdisciplinary research work is performed at two institutes of the ETH domain: at ETH Zurich and at Empa Dübendorf.
The main point of the efforts is the synthesis of inorganic nano-crystals and their self-assembly on multi-functional solid state structures. By developing a suitable design as well as by performing extensive characterization of the surface chemistry as well as the spacing of the nano-crystals, we aim to transfer the properties of individual nano-crystals into useful properties of solids based on nano-crystals. Finally, these research efforts will lead us to cost-effective and high throughput production processes for nano-structured materials for the application in energy generation and storage.
Publication in Nature Energy about Perovskite-CIGS-Tandem solar cells
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New World Record for flexible CIGS solar cells. More
Publication about Potassium induced CIGS surface modification published in Nature Materials
Publication about low temperature processing of CIGS solar cells published in Nature Materials